Thread-based microfluidic system for detection of rapid blood urea nitrogen in whole blood

This study develops a thread-based microfluidic device with variable volume injection capability and 3-dimensional (3D) detection electrodes for capillary electrophoresis electrochemical (CE-EC) detection of blood urea nitrogen (BUN) in whole blood. A poly methyl methacrylate (PMMA) substrate with concave 3D electrodes produced by the hot embossing method is used to enhance the sensing performance of the CE-EC system. Results show that the chip with 3D sensing electrodes exhibits a measured current response nine times higher and signal-to-noise ratio five times higher when compared to the peak responses obtained using a chip with conventional 2D sensing electrodes. In addition, the developed thread-based microfluidic system is capable of injecting variable sample volumes into the separation thread simply by wrapping the injection thread different numbers of times around the separation thread. The peak S/N ratio can be further enhanced with this simple approach. Results also indicate that the CE-EC system exhibits good linear dynamic range for detecting a urea sample in concentrations from 0.1 to 10.0 mM (R (2) = 0.9848), which is suitable for adoption in detecting the BUN concentration in human blood (1.78-7.12 mM). Separation and detection of the ammonia ions converted from BUN in whole blood is successfully demonstrated in the present study, with the developed thread-based microfluidic system providing a low-cost, high-performance method for detecting BUN in human blood.